Tip of the Month

3/14/2011 Liver Shunt (Portosystemic Shunt)

Normally in the fetus, the patent ductus venosus, also know as a shunt, is present. This shunt bypasses blood away from the liver to the placenta so that the blood for the fetus can be cleansed by the mother. Then, within three days after birth, once the fetus is born, the shunt closes, and the puppyís liver must clean the blood on its own. However, there are times, when the shunt does not close off. This is an abnormal vessel that allows the blood to bypass the liver not allowing the blood to get cleansed by one of the bodyís filters (the liver). This is called a liver shunt (a portosystemic shunt).

There are different types of liver shunts. Two of the main ones are known as intrahepatic shunt (inside the liver) and extrahepatic shunt (outside the liver). The intrahepatic shunt is commonly found in large breeds and tends to be much more difficult to operate. The extrahepatic shunt is usually easily operable and more commonly found in small breeds. As a vet assistant you may learn about these types of liver shunts.

A few clinical signs you may learn in a veterinary school include abnormal behavior after eating, pacing and aimless wandering, pressing their head against the wall or constantly rubbing their head, (the blood not being filtered causes ammonia build up which makes their head feel funny), constant illnesses, (since the liver is not filtering the blood, it causes toxicity in the blood making your pet constantly ill), episodes of apparent blindness, low weight gain, bad mouth odor, (young pets should have good breath), lethargic, not very active, decrease in appetite, crystals in the urine,(this is from the excess ammonia), and UTIís. Some dogs may show several clinical signs while others only show one. Furthermore, some dogs might not start showing any signs until they are older.

There are a variety of tests that could be done to diagnose a portosystemic shunt. An ultrasound can help identify the shunt. A variety of blood tests can also help support this diagnosis. The most common test to help diagnose a liver shunt is a bile acid test. Once your pet is diagnosed then you may begin treatment. Your pet will have to be on a low protein diet. Protein promotes toxicity in an animal that has a liver shunt. Giving your pet lactulose may also help. At first this may cause diarrhea but then it will immediately help to detoxify your petís system.

Your Veterinarian will choose the best treatment option. One option might be to operate and the other might be to medically manage your pet depending on what type of liver shunt it has. A scintigraphy will help determine if the shunt is intrahepatic or extrahepatic.

If surgery is the best option, then your dog will have to be as stable as possible. This involves your pet being on a low protein diet and on prescription medication such as antibiotics and lactulose. If you have questions about what kinds of food are low in protein, you can ask your veterinary assistant or vet tech. The antibiotics are used as bacteria to circulate in the blood. Normally it is removed by the liver, but in this case, it will bypass the liver.

After surgery, your pet might be in some pain for a few days. Then within the next four months, you will begin to notice weight gain, muscle development, improvement in general appearance, lots more energy and no more head rubbing. After four months, you might also have to redo the bile acid test to check on the surgery status. If the test results are normal then you can put your pet back on regular food. Surgery is normally the best option, and it has an overall success rate of 85.


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